Many electrical devices, such as heavy machinery or power tools (e.g., table saws, drill presses, hand tools, etc.) can be hazardous if used by untrained or inexperienced users. In a home, such devices can be particularly dangerous because they frequently attract the attention and curiosity of children who, being oblivious to the hazardous nature of such devices, may play with them and inadvertently cause serious injuries to themselves or others. In an industrial setting, use of such electrical devices may be restricted, as a matter of policy, to a small group of authorized users (e.g., those who are trained or otherwise qualified to use the electrical devices, etc.) in order to reduce the risk of serious injuries.
Other electrical devices, such as television sets, stereo equipment, and personal computers, for example, are sensitive to misuses such as repetitive actuation of power (on/oft) switches. Such misuse of a computer, for example, can cause damage to the hard disk drive thereof with the result that data stored on the hard disk drive may be corrupted or lost. This type of damage can be the result of inadvertent misuse by a child or intentional misuse by a vandal.
In addition, it may be desirable to restrict access to television sets and stereo equipment to prevent unsupervised children, for example, from watching television or listening to music or other programming altogether or simply from watching or listening at particular times without permission.
Several prior-art expedients have been developed to control the operation of electrical devices to provide limited access to such devices. One such expedient, disclosed in U.S. Pat. No. 5,434,368, issued Jul. 18, 1995, is an apparatus that includes an enclosure in which an electrical receptacle is provided for receiving a plug from an electrical appliance. The enclosure of that apparatus also houses an electrical switch which a user can use to manually control power to the electrical appliance. The enclosure is also provided with a cover that locks in place to block access to the underlying electrical switch. When a user of that apparatus wants to switch the power to the electrical appliance on or off, the user must unlock and remove the cover to expose the electrical switch and then manually toggle the switch to the desired "power on" or "power off" position. This multi-step procedure which the prior-art apparatus requires for turning the electrical appliance on and off is undesirably time-consuming and cumbersome. Moreover, installation of this prior-art apparatus may require an existing built-in electrical receptacle to be replaced which requires re-wiring and is also cumbersome. And many users of electrical devices are incapable of performing such re-wiring and may therefore be required to incur the possibly significant expense of hiring an electrician to perform the installation.
U.S. Pat. No. 5,592,032, issued Jan. 7, 1997, discloses a security electrical interrupt device that measures the amount of electrical supply current being drawn by an appliance and disconnects electric power to the appliance if an authorization code has not been entered. This device is used to limit use of certain electrical appliances, such as electric stoves, which have low-power components (e.g., a light, a timer, or a clock) and which also have high-power components (e.g., stove burners). The device enables the light, timer, and clock to be used, but the device turns off power to the appliance if a user attempts to use a burner, for example. In short, this device is useful only in connection with appliances operating at two or more different power levels and, even when used with appliances of that type, the device does not completely disconnect power therefrom. Further, this approach is not readily usable in connection with pre-existing electrical devices which are not equipped with such a device.
It is, therefore, desirable to provide an improved electrical lockout apparatus which overcomes most, if not all, of the preceding problems.